1. Field of the Invention
The present invention relates to a process for producing soybean and/or soy protein products. This process relates to a technique for removing undesirable odors and tastes from soybeans and/or soy protein products.
2. Description of the Prior Art
It is known that the constituents of soybeans and/or soy protein products which give rise to undesirable odors, taste and color in the same can be extracted or removed when soybeans, defatted soybeans and extracted soy protein and the like, are immersed into an organic solvent such as ethanol, propanol, alcohol-water, or alcohol-n-hexane. In this process, it is necessary to minimize organic solvent consumption and this can be achieved by recirculating solvent solution from the immersion bath to a solvent recovering means and then recycling the solvent to the extraction bath. However, during recirculation of the solvent, undesirable odors accumulate in the solvent, and such repeatedly processed organic solvent eventually imparts odors to soybean and/or soy protein products.
Various techniques have been tried to overcome this problem. For example, in the case of ethanol extraction, although soybean and/or soy protein products are freed of solvent after the extraction under a reduced pressure of 5 mm Hg at 80.degree. C. for 10 hours, the components which give rise to undesirable odors and tastes in the soy products and also the odor of ethanol can not be completely removed under the reduced pressure conditions. In another prior art technique the recirculated solvent can be refined with an active carbon or ion-exchange resin. However, undesirable odors can not be completely removed or the refining costs are very high. In yet another prior art method (U.S. Pat. No. 3,897,574), the components which give rise to undesirable odors and tastes in soy products are removed by distillation. However, it is difficult to remove all kinds of undesirable odors and taste components from the soy products by this method. Therefore, a need continues to exist for a satisfactory method by which constituents of undesirable odors and tastes can be removed from soy beans and soy protein products.